Printing methods which are dependent on attributes of the printed image support and corresponding printing devices

ABSTRACT

A method for operating a printer or copier in which at least one optical or mechanical attribute of the printed image support to be printed is detected using a sensor (steps  102, 104, 110 ). At least one printing parameter is given according to the sensor output signals (steps  106, 108, 112 ). The printed image support is then printed while using the printing parameters detected in such a manner.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention is directed to printing methods wherein a printimage carrier, for example paper, is printed upon employment of printingparameters that have been set and predetermined. The invention is alsodirected to printer devices or, respectively, copier devices for theimplementation of the printing or, respectively, copying methods. Theprinter devices are explained in greater detail below.

2. Description of the Related Art

Printing methods that, for example, work according to theelectrographic, magnetographic or some other non-mechanical principleare known. In an electrographic printing method, the printing parametersinclude the charge potential of the photoconductor, the auxiliarypotential in the development station and other physical setting pointsthat influence the printing process.

It is known to set the printing parameters dependent on the lightsensitivity, the age or the temperature of a photoconductor employed inthe printing. What is achieved by a control of the actual printingparameters is that the predetermined rated printing parameters to be setare also adhered to given disturbances, for example given fluctuatingambient em or altered atmospheric humidity, with the result that theprinting conditions remain the same. It has been shown, however, thatprint images of the same high print quality are not always produced evengiven identical printing conditions.

Japanese published application JP-08-058081 A discloses an ink jetprinter wherein the moisture content of the print image carrier isacquired. The amount of ink employed for printing is set dependent onthe acquired moisture content in order to avoid a “bleeding” of theprint image.

Japanese Published Application JP-06-115061 A discloses an ink jetprinter wherein the amount of ink employed in printing is to be setdependent on the absorbency of the paper, on the permeability or on thesurface temperature. A sensor electronically acquires the thickness ofthe fully saturated paper. Heating resistors that serve for the ejectionof ink droplets are driven dependent on the acquired thickness.

German Published Application DE 34 31 484 A1 explained a color ink jetprinter wherein, using an optical sensor, a distinction is made betweennormal paper and a transparent film to be printed. Dependent on theacquired print image carrier, fewer printing points per picture elementto be presented are generated in a first operating mode for normal paperthan when printing film.

German Letters Patent DE 40 17 850 C1 is directed to a method and anapparatus for regulating the radiation dose of laser radiation whenprocessing materials.

European Patent Document EP-A-0660589 discloses a method for operating aprinter, or copier. An input unit is provided in a first exemplaryembodiment into which the type of recording medium, for example normalpaper, bond paper OHP sheets (overhead paper), smooth paper or recyclingpaper, is manually input. This input is automated in further exemplaryembodiments in that an optical sensor acquires the transmission, thesurface condition or the thickness of the recording medium andautomatically determines the type of recording medium dependent on theidentified values. An optimization of the printing event is thenundertaken dependent on the identified type of recording medium in thatthe illumination level is modified. Further, an adaptation can ensue inview of the hue and the color saturation.

Patent Abstracts of Japan, vol. 1995, no. 09, 31 October 1995 & JP 07162695 A (Canon, Inc.), 23 Jun. 1995, discloses a color image processorwith whose assistance an optimum color balance can be achieved bymeasuring spectroscopic properties of a recording material. A sensoracquires the light that passes through a recording paper. An RGB sensormeasures the color parts of an image of an original master. A computercarries out an RGB correction.

U.S. Pat. No. 5,774,146 discloses an ink printing method with coloredink in order to print a multi-color image. A sensor acquires surfaceparameters, for example coefficients of friction, the surface roughness,the light reflection of the print paper or a combination thereof. Thetype of paper employed is then identified on the basis of the sensorsignals and printing parameters are defined.

SUMMARY OF THE INVENTION

An object of the present invention is to provide printing or,respectively, copying methods wherein the quality of the print images isimproved further. Another object of the invention is to provide printerdevices that print printed images with high printing quality.

This and other objects of the invention are provided by a method foroperating a printer or copier device, whereby at least one opticalproperty of the print image carrier to be printed with a print image isacquired with a sensor, at least one printing parameter is set dependenton the sensor output signal of the sensor, and whereby the print imagecarrier is printed in a printing event upon employment of the printparameter that has been set step, characterized in that, given ablack-and-white printing with gray levels, the gray scale value of theprint image carrier is acquired with the assistance of a brightnesssensor; and in that at least one printing parameter that influences thegeneration of the gray levels is set dependent on the output signal ofthe gray scale value sensor; in that a multi-level character generatoris employed when exposing a photoconductor in an electrographic printeror copier device; and in that the illumination energies of the charactergenerator allocated to specific light-coding values are set dependent onthe sensor output signal, whereby gray transformation relationships thatindicate the illumination energies allocated to the light-coding valuesdependent on the gray scale value are preferably employed, the graytransformation relationships belonging to specific sensor outputsignals.

The invention also provides a method for operating a printer or copierdevice, whereby at least one optical property of the print image carrierto be printed with a print image is acquired with a sensor, at least oneprinting parameter is set dependent on the sensor output signal of thesensor, and whereby the print image carrier is printed in a printingevent upon employment of the print parameter that has been set,characterized in that, given color printing, the color locus of theprint image carrier is acquired with the assistance of a color sensor;in that the rated color densities of the colors to be printed aredetermined with predetermined color transformation relationships thatallocate rated color densities for the color separations employed in theprinting to the acquired color loci; in that the transformationrelationships are empirically determined before the printing event, andare stored as analytical equations or as table in a memory of theprinter or, a respectively, copier device.

Further, the invention provides a method for operating a printer orcopier device, whereby at least one mechanical property of the printimage carrier to be printed with a print image is acquired with asensor, at least one printing parameter is set dependent on the sensoroutput signal of the sensor, and whereby the print image carrier isprinted in a printing event upon employment of the print parameter thathas been set, characterized in that, the roughness of the surface of theprint image carrier is acquired with a roughness sensor; in that thetoner quantity to be applied onto the print image carrier is setdependent on the output signal of the roughness sensor, whereby thecharge potential of a photoconductor collaborating in the printing eventand the auxiliary potential of an allocated development station aresimultaneously modified. The printing parameters may be modified suchthat the size of the picture elements of the print image on the printimage carrier remains approximately the same.

An additional aspect of the invention provides a method for operating aprinter or copier device, whereby at least one optical property of theprint image carrier to be printed with a print image is acquired with asensor, at least one printing parameter is set dependent on the sensoroutput signal of the sensor, and whereby the print image carrier isprinted in a printing event upon employment of the print parameter thathas been set, characterized in that the light scatter of the surface ofthe print image carrier is acquired with an optical sensor; in thatprinting parameters that determine the raster tonal value or,respectively, the gray scale value and/or the dimensions of fine printdetails are prescribed dependent on the acquired light scatter; in thata raster toner mark is printed onto the print image carrier; and in thatlight reflected and/or scattered back in the region of the raster tonermark is acquired with the optical sensor. This aspect is furthercharacterized in that the raster toner mark is applied upon employmentof printing parameters that had been previously defined dependent on thegray scale value or color locus of the print image carrier.

In a preferred embodiment, the method is implemented in anelectrophotographic printer. Specifically, the illumination energy of anillumination device for exposing a light-sensitive element, an auxiliarypotential in a developer unit for the application of toner particlesand/or the charge potential of the light-sensitive element are employedas printing parameters. In the method for operating a printer or copierdevice, the foregoing methods may be utilized in combination.

The invention also provides a printer or copier device, particularly forthe implementation of the method, having a printer unit for printing aprint image carrier according to predetermined printing parameters, asensor unit for acquiring at least one optical or mechanical property ofthe print image carrier to be printed, and a control unit that sets atleast one printing parameter dependent on the output signal of thesensor unit, when printing with gray levels, the gray scale value of theprint image carrier is acquired with the assistance of a brightnesssensor and at least one printing parameter that influences thegeneration of the gray levels is set dependent on the output signal ofthe gray scale value sensor given color printing, the color locus of theprint image carrier is acquired with the assistance of a color sensorand the rated color densities of the colors to be printed are determinedwith predetermined color transformation relationships that allocaterated color densities for the color separations employed in the printingto the acquired color loci, and/or in that the roughness of the surfaceof the print image carrier is acquired with a roughness sensor and thetoner quantity to be applied onto the print image carrier is setdependent on the output signal of the roughness sensor; whereby theprinting parameters are modified such that the size of the pictureelements of the print image on the print image carrier remainsapproximately the same; and/or the light scatter of the surface of theprint image carrier is acquired with an optical sensor; a raster tonermark is preferably printed onto the print image carrier; light reflectedor allowed to pass by the raster toner mark is acquired with the opticalsensor; and printing parameters that determine the raster tonal valueor, respectively, the gray scale value and/or the dimensions of fineprint details are prescribed dependent on the acquired light scatter.

The inventive methods are based on the perception that the properties ofthe print image carrier to be printed critically influence the printing.Print images with constantly high print quality and with constantprinted image impression for the viewer on print image carriers havingdifferent properties can only be generated when the influences of theseproperties on the print image are taken into consideration in theprinting event. In the inventive method, at least one optical ormechanical property of the print image carrier to be printed istherefore acquired with the assistance of a sensor. At least oneprinting parameter is then set dependent on the sensor output signal.What this measure achieves is that influences of the type of paperemployed, for example yellowish, rough environmental paper instead ofwhite, smooth paper, on the print quality and, thus, on the subjectiveimpression made on the viewer of the print image are taken intoconsideration and compensated.

In the method according to the present invention, the gray scale valueof the print image carrier is acquired with a brightness sensor whenprinting with gray levels. Moreover, at least one printing parameterthat influences the generation of the gray levels is set dependent onthe output signal of the gray scale value sensor. For example, thenumber of gray scale values that is presented given what is referred toas a multi-level character generator, as disclosed by U.S. Pat. No.5,767,888, is also retained unmodified given print image carriers havinga different gray scale value in that the illumination energies allocatedto specific light-coding values are set dependent on the output of thebrightness sensor. Gray transformation relationships belonging tospecific output signals of the brightness sensor are thereby preferablyemployed, the relationships indicating the illumination energiesallocated to the light-coding values being dependent on the gray scalevalue. What is achieved by modifying the illumination energies is that,independently of the gray scale value of the print image carrier, thesame number of gray levels remain distinguishable in the print imagebecause a variation of the gray scale values in the print image isopposed by the gray scale value of the print image carrier. What can beparticularly prevented is that a saturation appears given dark grayscale values that makes regions with these gray scale values appearblack. The dark gray tones thus remain distinguishable bothmensurationally as well as when viewed.

In the method according to a further aspect of the invention, the colorlocus of the print image carrier is acquired with the assistance of acolor sensor given color printing. Subsequently, the rated colordensities of the colors to be printed are determined with predeterminedcolor transformation relationships that allocate rated color densitiesto the acquired color locuss, these assuring that colors that correspondto the colors to be produced on white normal paper are generated in theprint image despite the color locus that deviates from white. Full-colorimages printed on a colored paper thus have the same number of colorsthat would arise on white paper without the correction. For example, thecolor densities of the four color separations yellow, magenta, cyan andblack are corrected. Similar to the gray scale value, differences in thecolor locus of the print image carrier lead to a modified number ofpresented color levels when a saturation given dark colors is notopposed. The differences in the color locus of the print image carrieralso influence the hue of the print image when the color transformationrelationships are not suitably selected.

In one development, the gray and color transformation relationships areempirically determined before the printing event and are stored in amemory of the printer or, respectively, copier, preferably as analyticalequations or as a table. In the empirical determination of thetransformation relationships, the corrections of the gray levels or,respectively, of the color separations are evaluated, this beingundertaken by an experienced printing technician dependent on thebrightness or, respectively, on the color of the paper.

As a critical property of the print image carrier, the roughness of theprint image carrier is acquired with the assistance of a roughnesssensor given the method according to another aspect of the invention.The amount of toner to be applied onto the print image carrier isinfluenced dependent on the output signal of the roughness sensor inthat, for example given an electrophotographic printing event, thecharge potential of the photoconductor and/or the auxiliary potential atthe development station is raised or, respectively, lowered. What thismeasure achieves is that more or fewer toner particles are depositedwithout modifying the boundaries of the pixels (picture elements). When,for example, the gray tones are generated with the assistance of arastering step, then fades at the edge of the raster area given roughpaper are prevented with a more intense application of toner. The grayscale value, defined as a ratio of covered and non-covered area, remainsconstant independently of the roughness of the print image carrier.

As a further property of the print image carrier, the light scatter ofthe print image carrier is acquired with an optical sensor in anotherdevelopment given the method according to yet a further aspect of theinvention. Light scatter and gray scale value are different propertiesof the print image carrier. When, for example, the printer device workswith a raster in order to present different gray tones, then the lightscatter of the print image carrier is acquired, for example, in that araster toner mark at which toner-free and toner-covered regionsalternate, for example in the fashion of a checkerboard pattern, isprinted on the print image carrier. After the raster toner mark is fixedin a fixing station, the raster toner mark is irradiated with lighthaving a predetermined intensity and the light remitted by the rastertoner mark is acquired with the optical sensor. The optical sensorcovers a region that averages over the light and dark areas of theraster toner mark. The region is selected of such a size thatstatistical fluctuations in the print image of the raster toner mark donot falsify the result of the acquisition. Printing parameters thatdetermine the raster tone value or, respectively, the gray scale valueand/or the dimensioning of fine print structures, for example finelines, are then set dependent on the acquired light quantity. Given anelectrophotographic printing event, for example, the charge potential ofthe photoconductor is varied given a constant auxiliary potential at thedevelopment station. For example, the raster in the raster toner markhas a rastering of 42 μm. When the raster toner mark has a size ofapproximately 1 cm², then the light scatter of the print image carriercan be acquired in a simple way because more or less light proceedsunder the covered toner regions of the raster and is absorbed thereatdependent on the dispersion properties of the print image carrier.

By acquiring the light quantity with the assistance of a raster tonermark, the gray scale value produced by the print image carrier and bythe toner image is also acquired. Since the gray scale value or,respectively, the raster toner value are also dependent on the grayscale value or, respectively, the color value of the surface of thepaper, these properties of the carrier material can also be indirectlytaken into consideration when the printing parameters are set dependenton the raster toner value determined with the raster mark.

In a development, the raster toner mark is applied upon employment ofprinting parameters that have been previously defined dependent on thegray location or, respectively, color locus of the print image carrierand/or dependent on the roughness of the print image carrier. In thisprocedure, the properties having the greatest influence on the printimage and, thus, on the impression of a viewer are taken intoconsideration first. Subsequently, the light scatter—which does not havea negligible influence on the print image—is taken into consideration.

The invention is also directed to printer or, respectively, copierdevices that, in particular, can be employed for the implementation ofthe inventive methods or their developments. The aforementionedtechnical effects also apply to the printer or, respectively, copierdevices.

BRIEF DESCRIPTION OF THE DRAWINGS

Exemplary embodiments of the invention are explained below on the basisof the attached drawings.

FIG. 1 is a schematic illustration of a printer device in perspectiveview.

FIG. 2 is a flowchart for a paper-dependent color printing method.

FIG. 3 is a flowchart for a color-dependent black-and-white printingmethod.

FIG. 4 is a diagram for illustrating various process characteristics.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 shows a schematic illustration of a high-performance printerdevice 6. The printer device 6 has a transport mechanism 10 that isarranged close to a transfer printing station 12 and conveys formcontinuous carrier material through the transfer printing station 12,wherein the charge image applied on a photoconductor drum 14 and inkedwith toner is transferred onto the carrier material with a corona device(not shown). Subsequently, the continuous form carrier material issupplied to a fixing station 16 wherein the toner image, which can stillbe smeared, is joined smear-proof to the carrier material with theassistance of pressure and temperature. As viewed in the transportdirection indicated by an arrow, a first deflection unit 18 thatconducts the continuous form carrier material to the transfer printingstation and can turn the continuous form carrier material over or merelyoffset it laterally dependent on the selected printing mode is arrangedpreceding the transfer printing station 12. A second deflection unit 20is arranged after the fixing station 16 as viewed in the transportdirection. The second deflection unit 20 stacks the printed continuousform carrier material and, likewise dependent on the selected printingmode, can also deliver the material to the first deflection unit 18.

FIG. 1 shows the printer 6 in a first printing mode, the simplex mode,wherein a web section 8 of the continuous form carrier material from astack 22 is supplied to the printing unit 12 by the first deflectionunit 18. After the printing step, the transport mechanism 10 transportsthe web section 8 in the direction of the fixing station wherein thetoner image is permanently bonded to the continuous form carriermaterial. Subsequently, the second deflection unit 20 stacks the websection 8 on a second stack 24.

The printer device 6 also contains a sensor unit 30 that is arrangedbetween the fixing station and the deflection unit 20. The sensor unit30 contains a plurality of sensors for acquiring the properties of thecontinuous form carrier material, i.e. of the continuous form paper. Theindividual sensors are explained below in conjunction with FIGS. 2 and3.

FIG. 2 shows a flowchart for a color printing method dependent onproperties of the paper, this beginning in step 100 after the paper hasbeen changed. In a following step 102, the color locus of the paper isacquired with a color sensor. This ensues with one of the device of theX-Rite company of Grandville, Mich., USA, as described in theirbrochures “The Colour Guide and Glossary” (1996) and “A guide tounderstanding Colour Communication” (1993). The color locus is definedaccording to the color standard CIE 1976 (L*a*b*) recommended by the CIE(Commission International de l'Eclairage) and mentioned in thebrochures, which is also referred to as CIELAB.

In the following method step 104, the roughness of the paper to beprinted is acquired with a commercially available roughness sensor, forexample a paper roughness sensor according to Bendtsen. In this method,the roughness is identified in that air is suctioned in with a hollowsensor placed on the paper that comprises air entry holes on thatsurface placed on the paper. The quantity of air sucked in in ml/min isthen a measure for the roughness of the paper.

Subsequently, a compensation with respect to the paper color locus isimplemented in a method step 106 when the paper color locus determinedin method step 102 deviates from a predetermined reference color locus.In the printing method explained with reference to FIG. 2, the colorseparations yellow, magenta, cyan and black are employed in anelectrophotographic printer. In step 106, a color transformation curveis selected for the paper color locus of the paper to be printed,correction factors for correcting reference color densities for the fourcolor separations being determined with the color transformation curve.The corrected color densities are stored for the printing event as ratedvalues for a color separation density control.

In a following method step 108, the influence of the roughness of thepaper is compensated when the roughness identified in the method step104 deviates from a reference roughness. The roughness of smooth paperis employed as a reference roughness, i.e. paper having a roughnessvalue according to Bendtsen of less than 100 ml/min. Given a smoothpaper surface, less toner per surface area is required for a specificinking than given rough paper. For compensating the roughness in methodstep 108, the charge potential of the photoconductor and the auxiliarypotential in the developing station are therefore simultaneouslymodified. What is achieved with this measure is that more toner materialis deposited per pixel area but the respective character or rastercontour is not modified. The charge potential of the photoconductor andthe auxiliary potential VBias determined in method step 108 are storedin a memory of the printer device 6.

The light scatter of the paper to be printed is acquired in a methodstep 110. To that end, a raster toner mark is printed on the paper,whereby the printing parameters identified in method steps 106 and 108are employed. The raster toner mark is preferably irradiated with alight source after the fixing step in a fixing station. The lightreflected by the raster toner mark is acquired with a light sensor thatworks in an integrating fashion. Given employment of a reference paper,a reference value DZ of the light scatter is acquired. Given a paperwhose light scattering properties deviate from those of the referencepaper, a light scatter value D deviating from the reference value DZ isacquired given what is otherwise the same toner distribution on thepaper.

In a method step 112, the influence of the light scatter of the paper onthe print image is compensated when the light dispersion value Dacquired in method step 110 deviates from the reference value DZ. Thecompensation ensues in that the charge potential VC of thephotoconductor is modified given an unmodified auxiliary potentialVBias. What are thus varied are printing parameters that determine theraster tonal value of the images and the dimensions of fine printedstructure such as, for example, the line width. A print image arises onthe respectively employed paper that corresponds to a print imageprinted on the reference paper under standard conditions. When the lightdispersion value is lower than the reference value DZ, then the printingparameters are varied such that the raster tonal value and the detaildimensions are increased. For example, the charge potential VC islowered given an unmodified auxiliary potential VBias.

In a method step 114, the method for determining the printing parametersthat are dependent on the paper is ended. The printing parameters thathave been identified are then retained in the following printing events.

FIG. 3 shows a flowchart for a paper-dependent black-and-white printingmethod. The method begins in a step 200.

In a method step 202, the gray scale value of the paper to be printed isacquired with a brightness sensor. Simultaneously or subsequently, thepaper roughness is acquired in a method step 204, as already explainedabove for the method step 104. Subsequently, the influence of the grayscale value of the paper on the print image is compensated in a methodstep 206. It is thereby taken into consideration that, given non-whitepaper, the gray scale values in the print image are shifted overall tohigher values compared to the same gray scale values on white paper. Theblack-and-white print image printed on non-white paper is matched to aprint image printed on white paper in that parameters of the printingprocess are modified such that the same number of gray levels remainsdistinguishable. In the exemplary embodiment, a multi-level charactergenerator that, for example, is disclosed by U.S. Pat. No. 5,767,888 isemployed for the printing. The overall process characteristic of theprinting process is deformed in that the light-coding values of themulti-level character generator have corrected illumination energiesallocated to them. This ensues either individually for each light-codingvalue or for all light-coding values in the same relationship. Thecorrected illumination energies are stored for the further printingprocesses.

In a method step 208, the influence of the roughness of the paper istaken into consideration such as explained above for the method step108. In method step 210, the light scatter of the paper is acquired uponemployment of a raster toner mark that is printed onto the paper withthe printing parameters determined in method steps 206 and 208. Thecompensation of the influence of the light scatter of the paper on theprint image ensues in method step 212 as explained above for the methodstep 112. The method is ended in the method step 214.

In other exemplary embodiments, which are not shown, the methodsexplained on the basis of FIGS. 2 and 3 are also implemented after theprinter device 6 is turned on. As a result of this measure, theproperties of paper that has been placed therein with the printed device6 turned off can also be taken into consideration.

In all methods being set forth, the employment of an additional sheet isavoided with the light scatter as determined without a raster tonermark. The explained methods are then implemented before the first sheetof paper is printed. The printing parameters that are thereby determinedare then already employed when the print image is applied onto the firstsheet.

Given the methods explained on the basis of FIGS. 1 through 3, surfaceproperties of the print image carrier to be printed are acquired.Sensors and receivers are preferably located at one side of the printimage carrier to be printed. Thus, the sensor unit 30 shown in FIG. 1 isarranged lying opposite that print side of the web section to beprinted. Thus, either mechanical or optical surface properties of theprint image carrier are acquired. The optical properties are closelyrelated to the light remission, i.e. to the light cast back from thesurface. The light remission is essentially defined by the reflectedradiation, the radiation scattered back at the print image carrier andthe color composition of the remitted light.

FIG. 4 shows a diagram 250 related to the presentation of variousprocess characteristics 252 through 258. The rated values for the inkingare entered on the x-axis 260. The actual values for the inking of theprint image printed on the print image carrier, for example the paper,are shown on the y-axis. The numerical values shown on the x-axis 260or, respectively, on the y-axis 262 are without units since they are amatter of relative logarithmic units. Given the employment of paper witha rated white with which all colors would be reflected at 100%, anoptimally set printing process leads to the process characteristic 252.The process characteristic 252 begins in the zero point of the diagram250 shown in FIG. 4 and ends in the intersection of the x-value 1.0 andthe y-value 1.0. The process characteristic 252 is linear between thestart and end point.

When paper that has a gray scale value or, respectively, a color thatdeviates from the rated white is employed, then unprinted regionsalready have the inking 0.2. The inking corresponds to a specific grayscale value. Moreover, the process characteristic 252 is shifted towardhigher inkings of the paper, illustrated by the process characteristic254. The other paper properties such as roughness and light scatterbehavior also influence the gray scale value arising on the paper. Giventhe process characteristic 252, all image regions appear with rated grayscale values above 0.8 black. A saturation occurs in this region andgray scale values cannot be distinguished from one another in thisregion. For a best possible image reproduction, all gray scale values tobe reproduced in the image must be uniformly distributed over theavailable range from 0.2 through 1.0. A process characteristic asillustrated by the process characteristic 256 in FIG. 4 is requiredtherefor. A printing process set according to the process characteristic256 yields the process characteristic 258 when printed on paper withrated white, this being shifted such relative to the processcharacteristic 256 that it begins in the origin of the diagram 250 andends in the intersection of the x-value 1.0 and of the y-value 0.8. Whenthe same toner image is printed on paper that deviates from the ratedwhite, then, for example given black-and-white printing, the gray scalevalues of paper and toner image superimpose. The process characteristic258 arise due to the superimposition.

In one exemplary embodiment, correction values for specific processparameters of the printing process are determined such that a pluralityof gray scale raster marks are printed on the paper to be employed,being initially printed in a first part of the method with apredetermined printing process, for example with the printing processfor paper having the color rated white. Subsequently, the raster markgray scale values achieved on the paper as well as the gray scale valueof the unprinted paper are acquired with a brightness sensor. Thecorrection values for the printing process parameters can be determinedwith the assistance of the acquired values, this being shown in FIG. 4by circles on the process characteristic 254. Subsequently, thecorrected parameters are stored for the further printing method in acontrol unit of the printer, of the printer device 6.

Some possibilities for influencing the electrophotographic printingprocess are indicated in the following patent documents:

German Patent Document DE 198 59 140, printer devices working with atleast three brightness levels as well as methods to be implementedtherewith for determining printing parameters, particularly therelationships shown in FIG. 6 of this patent document;

German Patent Document DE 198 59 094, method for printing with amulti-level character generator as well as a printer device, as exampleof the determination of correction factors with which a predeterminedcharacteristic can be achieved;

German Patent Document DE 198 59 93, method for improved theelectrographic printing of image details as well as a printer deviceworking according to this method, as an example of the correction of thecharge of the photoconductor as a result of modified illuminationenergies; and

German Patent Document DE 196 12 637, method for optimizing thegeneration of a charge image.

The possibilities indicated in the references for influencing theprinting process are also recited in the subsequent applications basedon these applications.

The determination of the correction values is implemented in a pluralityof matching steps in order to better approach the target characteristic,see, for example, the process characteristic 258. The plurality of grayscale raster marks is selected such that an adequate approach to thetarget characteristic can be achieved with a reasonable acquisition andcalculating outlay. Gray scale values that have not been acquired can bedetermined by interpolations. In the simplest case, a process matchingcan also ensue without a test printing of raster gray scale values andwithout acquisition of the gray scale value of these raster marks. Tothat end, only the gray scale value of the unprinted paper is measuredwith the brightness sensor. The process parameter corrections are thendetermined from this measured value.

The matching for the color printing ensues similar to that givenblack-and-white printing. Thus, the sub-processes of the colorseparations needed for the color printing are successively adapted tothe paper properties, i.e., for example, for color separations of thecolors yellow, magenta, cyan and black. Instead of the brightness sensorfor measuring the gray scale values of the raster marks and of theunprinted paper, a color sensor is employed in color printing formeasuring the inking values of the raster marks and of the paper, see,for example, the aforementioned color sensors of the X-Rite company.

The matching process in the color printing can be simplified in that,particularly given not especially high quality demands, the matching iseliminated from one or more sub-processes. For example, only the colorseparation for black and one further color is adapted when only what isreferred to as a highlight color printing is to be implemented.

Although other modifications and changes may be suggested by thoseskilled in the art, it is the intention of the inventor to embody withinthe patent warranted hereon all changes and modifications as reasonablyand properly come within the scope of their contribution to the art.

What is claimed is:
 1. A method for operating a printer or copierdevice, comprising the steps of: acquiring at least one optical propertyof the print image carrier to be printed with a print image with asensor; setting at least one printing parameter dependent on an outputsignal of the sensor; printing the print image carrier in a printingevent utilizing the at least one print parameter that has been set;acquiring light scatter of a surface of the print image carrier with anoptical sensor; prescribing printing parameters that determine one of araster tonal value and a gray scale value and dimensions of fine printdetails dependent on the acquired light scatter; printing a raster tonermark onto the print image carrier; and acquiring light that is one ofreflected and scattered back in a region of the raster toner mark withthe optical sensor.
 2. A method as claimed in claim 1, wherein theraster toner mark is applied utilizing the at least one printingparameter that has been previously defined dependent on one of a grayscale value and a color locus of the print image carrier.
 3. A printeror copier device, comprising: a printer unit for printing a print imagecarrier according to predetermined printing parameters; a sensor unitfor acquiring at least one optical or mechanical property of the printimage carrier to be printed; a control unit that sets at least oneprinting parameter dependent on an output signal of the sensor unit;given gray scale printing, a brightness sensor which acquires a grayscale value of the print image carrier so that at least one printingparameter that influences generation of the gray levels is set dependenton an output signal of the brightness sensor; given color printing, acolor sensor which acquires a color locus of the print image carrier tothat rated color densities of colors to be printed are determined withpredetermined color transformation relationships that allocate ratedcolor densities for color separations employed in the printing to theacquired color loci; a roughness sensor to sense roughness of a surfaceof the print image carrier so that toner quantity to be applied onto theprint image carrier is set dependent on an output signal of theroughness sensor; a control to modify printing parameters such that sizeof picture elements of the print image on the print image carrierremains approximately the same; an optical sensor to sense light scatterof the surface of the print image carrier; a raster toner mark isprinted onto the print image carrier so that light reflected the rastertoner mark is acquired with the optical sensor; printing parameters thatdetermine at least one of raster tonal value and gray scale value anddimensions of fine print details being prescribed dependent on acquiredlight scatter.